Investigation of flow properties in natural streams using the entropy concept

This paper examines the discharge and velocity distributions in natural open channel flows using the entropy theory. Flow measurements were carried out at four different cross‐sections in central Turkey. The mean and maximum velocities at these stations exhibited a linear distribution and the entropy parameter was calculated to be M=1.31. Using this value, discharges for all flow conditions were calculated as a function of the measured maximum velocities (u_max). It was observed that the u_max/H and z_max/H ratios remained relatively constant when 0.2≤y/T≤0.8, especially for the wider channels. Using these constant values for each station, u_max and z_max could be determined solely as a function of the water depth H. Although the calculated velocities were higher than those measured at some verticals, the entropy‐based approach presents an attractive alternative to the traditional flow‐measurement techniques for the determination of flow properties because of its simplicity and quick application.     

Effects of circumferential pick spacing on boom type roadheader cutting head performance

Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force–balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads.     

IEEE 802.16J relay-based wireless access networks: an overview [recent advances and evolution of WLAN and WMAN standards]

Multihop wireless systems have the potential to offer improved coverage and capacity over single-hop radio access systems. Standards development organizations are considering how to incorporate such techniques into new standards. One such initiative is the IEEE 802.16j standardization activity, adding relay capabilities to IEEE 802.16 systems. This article provides an overview of this relay-based technology, focusing on some of the most pertinent aspects. In particular, the different modes of operation (transparent and non-transparent), framing structures, and network entry procedures are described. Some consideration of the issues in designing such systems is then given, which highlights when different features within the standard are most appropriate. As these systems are very new, many open issues remain to be resolved.     

Energy output estimation for small-scale wind power generators using Weibull-representative wind data

Estimation of energy output for small-scale wind power generators is the subject of this article. Monthly wind energy production is estimated using the Weibull-representative wind data for a total of 96 months, from 5 different locations in the world. The Weibull parameters are determined based on the wind distribution statistics calculated from the measured data, using the gamma function. The wind data in relative frequency format is obtained from these calculated Weibull parameters. The wind speed data in time-series format and the Weibull-representative wind speed data are used to calculate the wind energy output of a specific wind turbine. The monthly energy outputs calculated from the time-series and the Weibull-representative data are compared. It is shown that the Weibull-representative data estimate the wind energy output very accurately. The overall error in estimation of monthly energy outputs for the total 96 months is 2.79%.     

Alternative regional specification and convergence of U.S. regional growth rates

We apply absolute beta convergence techniques to cross sectional per capita income data for alternative specifications of U.S. regions in order to detect whether U.S. regional growth rates are converging over relatively recent time periods. We also explore whether estimates of convergence differ between economic and political region specifications. We show that convergence of growth rates across regions of the U.S. has continued in modern times (1969–1997) for almost any regional specification and for all time frames considered. We do find, however, some difference in convergence rates between economic and political regions. Convergence coefficients, however, are remarkably similar across alternative economic region specifications. An earlier version of this paper was presented in February 2003 at the 42nd annual meetings of the Western Regional Science Association in Rio Rico, Arizona. We would like to thank our session participants in Rio Rico and three anonymous referees for helpful comments. Any remaining errors or oversights, however, are entirely our responsibility.     

Feature tracking and matching in video using programmable graphics hardware

This paper describes novel implementations of the KLT feature tracking and SIFT feature extraction algorithms that run on the graphics processing unit (GPU) and is suitable for video analysis in real-time vision systems. While significant acceleration over standard CPU implementations is obtained by exploiting parallelism provided by modern programmable graphics hardware, the CPU is freed up to run other computations in parallel. Our GPU-based KLT implementation tracks about a thousand features in real-time at 30 Hz on 1,024 × 768 resolution video which is a 20 times improvement over the CPU. The GPU-based SIFT implementation extracts about 800 features from 640 × 480 video at 10 Hz which is approximately 10 times faster than an optimized CPU implementation.     

Gain studies of 1.3-μm dilute nitride HELLISH-VCSOA for optical communications

The hot electron light emitting and lasing in semiconductor heterostructure-vertical-cavity semiconductor optical amplifier (HELLISH-VCSOA) device is based on Ga_0.35In_0.65 N_0.02As_0.08/GaAs material for operation in the 1.3-μm window of the optical communications. The device has undoped distributed Bragg reflectors (DBRs). Therefore, problems such as those associated with refractive index contrast and current injection, which are common with doped DBRs in conventional VCSOAs, are avoided. The gain versus applied electric field curves are measured at different wavelengths using a tunable laser as the source signal. The highest gain is obtained for the 1.3-μm wavelength when an electric field in excess of 2 kV/cm is applied along the layers of the device.     

Negative attitudes to transition in post-communist Albania and acute coronary syndrome.

Objective: The authors assessed the association of acute coronary syndrome (ACS) with attitudes to the socioeconomic aspects of rapid change in transitional Albania. Design: A population-based case–control study conducted in Tirana, Albania, in 2003–2006 included 467 nonfatal ACS patients (370 men, 97 women; 88% response) and a population-sampled control group (469 men, 268 women; 69% response). Main Outcome Measures: Reaction to transition was assessed as a composite score of 3 items capturing attitudes toward socioeconomic aspects of transition in Albania. Results: Using logistic regression, there was a strong linear relationship of the attitude score with ACS. When categorized as negative, intermediate, or positive attitudes, the age- and sex-adjusted odds ratio (OR) for the negative versus positive categories was 3.0; 95% confidence interval (CI) = 2.1, 4.3; p for linear trend     

Performance Assessment of a Potato Crisp Frying Process

Frying is a common and popular cooking method, which has been widely used in food manufacturing, though it is a very energy-intensive process. Energy analysis has been commonly used to assess the performance of fryers. In this study, we attempted to exergetically assess the performance of a potato crisp frying system, which consists of three main components, a combustor, a heat exchanger, and a fryer. In the analysis, we utilized the actual operational data obtained from the literature. We determined exergy destruction in each system component and the whole system. We calculated universal and functional exergy efficiency values for the system components and compared them with each other. We also undertook a parametric study to investigate how the overall cycle performance was affected by changing the reference environment temperature and some operating conditions. We illustrated the exergy results through the Grassmann (exergy loss and flow) diagram. We calculated the universal exergetic efficiency values of 58, 82, and 77% for the combustor, heat exchanger, and fryer, respectively, with a universal exergetic efficiency value of 4% for the whole frying system. We found that the fryer had the highest functional exergetic efficiency value of 74%, followed by the heat exchanger with 47% and the combustor with 0.08%.     

Photoinduced electron transfer mechanism between green fluorescent protein molecules and metal oxide nanoparticles

Green fluorescent protein (GFP) molecules are attached to titanium dioxide and cadmium oxide nanoparticles via sol–gel method and fluorescence dynamics of such a protein–metal oxide assembly is investigated with a conventional time correlated single photon counting technique. As compared to free fluorescent protein molecules, time-resolved experiments show that the fluorescence lifetime of GFP molecules bound to these metal oxide nanoparticles gets shortened dramatically. Such a decrease in the lifetime is measured to be 22 and 43 percent for cadmium oxide and titanium dioxide respectively, which is due to photoinduced electron transfer mechanism caused by the interaction of GFP molecules (donor) and metal oxide nanoparticles (acceptor). Our results yield electron transfer rates of 3.139×10⁸ s⁻¹ and 1.182×10⁸ s⁻¹ from the GFP molecules to titanium dioxide and cadmium oxide nanoparticles, respectively. The electron transfer rates show a marked decrease with increasing driving force energy. This effect represents a clear example of the Marcus inverted region electron transfer process.